The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
ACK acknowledge
BS base station
BW bandwidth
CAZAC constant amplitude zero autocorrelation
CCE control channel element
CP cyclic prefix
CQI channel quality indicator
DL downlink (eNB towards UE)
eNB E-UTRAN Node B (evolved Node B)
EPC evolved packet core
E-UTRAN evolved UTRAN (LTE)
FDD frequency division duplex
FDMA frequency division multiple access
HARQ hybrid automatic repeat request
LTE long term evolution of UTRAN (E-UTRAN)
MAC medium access control (layer 2, L2)
MM/MME mobility management/mobility management entity
NACK negative acknowledge
Node B base station
OFDMA orthogonal frequency division multiple access
O&M operations and maintenance
PCFICH physical control format indicator channel
PDCCH physical downlink control channel
PDCP packet data convergence protocol
PDU protocol data unit
PHY physical (layer 1, L1)
PRB physical resource block
PUCCH physical uplink control channel
RLC radio link control
RRC radio resource control
RRM radio resource management
S-GW serving gateway
SC-FDMA single carrier, frequency division multiple access
SR scheduling request
UE user equipment, such as a mobile station or mobile terminal
UL uplink (UE towards eNB)
UTRAN universal terrestrial radio access network
ZAC zero autocorrelation
A proposed communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently under development within the 3 GPP. The current working assumption is that the DL access technique will be OFDMA, and the UL access technique will be SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.3.0 (2007-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8), incorporated by reference herein in its entirety.
FIG. 1 reproduces FIG. 4 of 3GPP TS 36.300, and shows the overall architecture of the E-UTRAN system 2. The E-UTRAN system 2 includes eNBs 3, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs 3 are interconnected with each other by means of an X2 interface. The eNBs 3 are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to a S-GW by means of a S1-U interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
From a PUCCH resource allocation point of view, four basic types of control signals can be transmitted:                ACK/NACKs of dynamically scheduled DL data (PUCCH format 1a and 1b);        periodic CQIs (PUCCH format 2, 2a, and 2b);        SR indicators (PUCCH format 1); and        ACK/NACKs of persistently scheduled DL data (PUCCH format 1a and 1b).        
Reference with regard to various PUCCH formats can be made to subclauses 5.4.1, 5.4.2 and 5.4.3 of 3GPP TS 36.211 V8.1.0 (2007 November) Technical Specification 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8), incorporated by reference herein in its entirety.
For dynamic ACK/NACKs, it has been agreed that the PUCCH resource to be used is implicitly derived from the PDCCH CCE index. Due to the implicit mapping, the ACK/NACK channel on the PUCCH should be pre-configured by higher layer signaling. This pre-configuration is typically referred to as ACK/NACK channelization. The details for implicit mapping of dynamic ACK/NACKs have been agreed to in 3GPP.
The basic principle of implicit channelization of dynamic ACK/NACKs is to have a one-to-one mapping to the lowest CCE index. The total number of CCEs depends on the system bandwidth and on the number of OFDM symbols allocated for control signaling in a DL subframe, which is signaled in each subframe using the PCFICH (1, 2, or 3 OFDM symbols/subframe). This means that, for example, with a 20 MHz system bandwidth the number of CCEs can be as many as 80 if three OFDM symbols are allocated for control signaling in a subframe. However, if the PCFICH=1 there is a significantly smaller number of CCEs. This implies that the required amount of UL resources for the dynamic (implicit) ACK/NACKs can vary dynamically from one subframe to another.
It has also been agreed that the PUCCH resources used for periodic CQI transmission (e.g., the cyclic shift), the SR indicator and the persistent ACK/NACK are explicitly configured. Furthermore, it has been agreed that the PUCCH PRBs with CQI are to be placed on the outermost PRBs next to band edges, followed by the dynamic ACK/NACKs.
Although there is a general agreement concerning the resource allocation of each of these types of PUCCH signals, the specific details of how to allocate the PUCCH resources for SR and persistent ACK/NACK have not yet been worked out.
As noted above, the current agreement in 3GPP is to allocate resources for CQI to the outermost PRBs next to band edges, and to allocate the dynamic ACK/NACKs next to the CQI resources. The principle is shown in FIG. 3. The number of CQI PRBs is signaled via higher layer using a parameter NRB(2) (NRB(2)=7 in the example of FIG. 3).
Further, the CQI PRB having a largest index can be split to accommodate both CQIs and dynamic ACK/NACKs with parameter Ncs(1). The resources for the dynamic ACK/NACKs are placed next to the CQI resources. An ACK/NACK index of a certain UE can be directly derived from its lowest CCE index, the number of PDCCH CCEs, and hence the number of implicitly allocated dynamic ACK/NACK resources scales, according to the system bandwidth and the value of PCFICH.
The SR and persistent ACK/NACK configuration have not been discussed in detail in the 3GPP. The basic assumption has been, however, that a separate resource pool (e.g. one or more PRBs) is semi-statically assigned for the SR and persistent ACK/NACK (see FIG. 3). However, one significant drawback of this approach is that due to the dynamically varying PCFICH and hence the (possibly constantly) changing number of dynamic (implicit) ACK/NACK resources/channels, there will exist an unused gap between the dynamic ACK/NACK channels and the SR and persistent ACK/NACK channels when PCFICH<3. This leads to increased UL overhead and/or spectrum fragmentation. Changes in the parameters NRB(2) (number of PRBs reserved for CQI) and/or Ncs(1) will make the PUCCH space even more dynamic. The alternative, that is keeping Ncs(1) and NRB(2) essentially constant, has the disadvantage of causing over-dimensioning of the periodic CQI resources, which is also wasteful of the spectrum.